1. Field of Invention
The present invention relates to a method of transmission through single wire, especially a method using simple signal transmission protocol to transmit complicated information through single wire.
2. Description of Related Art
For communication between two circuits such as between a power management device and another device, popular communication interfaces such as I2C, SPI, and SMBUS require at least two wires, one for data and another for clock signal. It would be beneficial if data and clock signal can be transmitted by one single wire, because the circuit pin number can be reduced, and it is not necessary to synchronize the clock signals between the receiving circuit and the transmitting circuit. U.S. Pat. Nos. 7,127,631 and 7,080,266 disclose a single wire transmission method as shown in FIG. 1, wherein when the receiving circuit detects a rising edge of the signal EN/SET transmitted through the signal wire, it is enabled to receive data as shown by the signal ENABLE, and the receiving circuit generates a clock signal (CLOCK) according to the signal EN/SET. A counter of the receiving circuit begins to count the rising edges (1˜n) of the signal EN/SET. When the receiving circuit detects a falling edge of the signal EN/SET, it begins to count a time-out period. If no rising edge is detected within the time-out period, the signal ENABLE is stopped; the counter is reset, and the clock signal CLOCK is stopped.
The aforementioned prior art patents count the rising edges from low level to high level, and the count represents the transmitted information. Thus, to transmit a number n, n rising edges have to be transmitted. The larger the transmitted number is, the more rising edges are needed, and the transmission period (bit length) is longer. Apparently, this method is inconvenient for transmitting a very large number, and because the length of the transmission period is not fixed, it causes some problems in certain applications.
In view of foregoing, the present invention provides a method of transmission through single wire, which is capable of transmitting complicated information through single wire by simple protocol.